Effect of Pyrazole and Dexamethasone Administration on Cytochrome P450 2E1 and 3A Isoforms in Rat Liver and Kidney: Lack of Specificity of p-Nitrophenol as a Substrate of P450 2E1

• Published in: Alcoholism, clinical and experimental research clinical and experimental research, 1998-05, Vol.22 (3), p.652-657
• Main Authors: Zerilli, Alain, Lucas, Danièle, Dreano, Yvonne, Picart, Daniel, Berthou, François
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Aryl Hydrocarbon Hydroxylases; Biological and medical sciences; Cytochrome P-450 CYP2E1 - metabolism; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System - metabolism; Dexamethasone - pharmacology; Enzyme Induction - drug effects; Enzyme Inhibitors - pharmacology; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Key Words: P450 2E1; Kidney; Kidney - drug effects; Kidney - enzymology; Liver; Liver - drug effects; Liver - enzymology; Male; Nitrophenols - pharmacokinetics; Oxidoreductases; Oxidoreductases, N-Demethylating - metabolism; p-Nitrophenol; P450 3A; Pyrazoles - pharmacology; Rats; Rats, Wistar; Substrate Specificity
• ISSN: 0145-6008; 1530-0277
• DOI: 10.1111/j.1530-0277.1998.tb04307.x

The induction effects of pyrazole and dexamethasone (known to be specific to P450 2E1 and 3A enzymes, respectively), given alone or simultaneously, were studied in rat liver and kidney microsomes. Pyrarole treatment induced the catalytic activity and the amount of P450 2E1 enzyme in both organs. Immunoreactive P450 2E1 and 4‐nitrophenol 2‐hydroxylation increased 8‐ and 13‐fold, respectively (versus control), in the kidney, but only 2.4‐ and 2.7‐fold (versus control) in the liver after pyrazole treatment. As assessed by nifedipine oxidation activity, dexamethasone treatment increased the P450 3A catalytic activity approximately 4‐fold (versus control) in the liver, but not in the kidney, suggesting that P450 3A was not inducible in the kidney. Pyrazole decreased P450 3A activity in the liver but did not modify it in the kidney. A combination of both chemicals induced both enzymes, but to a lesser extent than treatment with each single chemical compound. Furthermore, the 2‐hydroxylation of p‐nitro‐phenol, considered one of the most specific substrates for monitoring the level of P450 2E1, was mediated also by P450 3A, at least in dexamethasone‐treated rats. Finally, this experimental work demonstrated that P450 3A induction is organ‐specific, and it also demonstrated the lack of specificity of p‐nitrophenol as a P450 2E1 substrate.